This project is funded by the NIH Intramural AIDS Targeted Antiviral Program. It involves an investigation of the activation of HIV-1 gene expression by stresses such as DNA-damaging agents. Treatment of human cells with DNA-damaging agents, such as UV radiation, can lead to the activation of latent virus and to increased virus production. This activation is probably mediated by multiple mechanisms including the induction of a cellular Tat-like factor and the induction of at least one and probably more proteins that bind to specific elements in the HIV promoter. Current efforts focus on two areas. In the first. activation of the HIV-1 promoter by genotoxic stress is being studied primarily by the use of HIV-promoter CAT (chloramphenicol acetyltransferase) reporter gene constructs in various cell lines. We have confirmed the work of Valerie (Valerie, K. Delers, A. Bruck, C. Thiriart, C, Rosenberg, H. Debouck, C. Rosenberg, M. Activation of human immunodeficiency virus type 1 by DNA damage. Nature 1988;333:78-81.) that stably-integrated HIV-CAT constructs are much more strongly UV-inducible than in transient assays in HeLa cells; this finding has been extended to a variety of other mammalian cells. Efforts are underway to identify elements in the promoter that contribute to this DNA-damage responsiveness. In collaboration with D. Yarosh, activation of stably-integrated HIV-CAT has been found after exposure of cells to conditioned medium from UV-treated cells. Efforts are underway to identify the soluble factors that are required for this transactivation. The second area involves cellular TAR-binding proteins which may play a role in HIV activation in cells after genotoxic stress. UV-induction of HIV-CAT occurs in cells that lack Tat. Cellular proteins with Tat-like function may contribute to this activation and will be investigated.